Fiber tractography using entropy spectrum pathways

Abstract

A method for fiber tractography processes multi-shell diffusion weighted MRI data to identify fiber tracts by calculating intravoxel diffusion characteristics from the MRI data. A transition probability is calculated for each possible path on the lattice, with the transition probability weighted according the intravoxel characteristics. Entropy is calculated for each path and the paths are ranked according to entropy. A geometrical optics algorithm is applied to the entropy data to define pathways, which are ranked according to their significance to generate a map of the pathways.

Description

RELATED APPLICATIONS[0001]This claims the benefit of the priority of Provisional Application No. 62 / 066,780, filed Oct. 21, 2014, which is incorporated herein by reference in its entirety.GOVERNMENT RIGHTS[0002]This invention was made with government support under Grant MH096100 awarded by the National Institutes of Health and Grant DBI-1147260 awarded by the National Science Foundation. The government has certain rights in the invention.FIELD OF THE INVENTION[0003]The present invention relates to a method for the characterization of connectivity within complex data and more particularly to a method for identifying neural pathways within DW-MRI data.BACKGROUND[0004]Magnetic Resonance Imaging (MRI), or nuclear magnetic resonance imaging, is commonly used to visualize detailed internal structures in the body. MRI provides superior contrast between the different soft tissues of the body when compared to x-ray computed tomography (CT). Unlike CT, MRI involves no ionizing radiation becau...

AI Technical Summary

Benefits of technology

[0023]The present invention provides a method for the simultaneous estimation of local diffusion and global fiber tracts. The ESP method can be further enhanced by introducing a new approach to include multi-scale and multi-modal diffusion field into a scalar information entropy flow.

[0024]For the first time in neuroscience, the ESP method provides for the application of probability conservation to obtain fiber tracts through ray tracing of the convective modes guided by a global structure of the entropy spectrum coupled with small scale local diffusion. The method uses a novel approach to incorporate global information about multiple fiber crossings in each individual voxel and rank it in a scientifically rigorous manner. The method exploits six dimensional space for tracking neurofibers, providing a significant improvement over the three-dimensional positional tracking methods currently in use. The method avoids the need for an expensive front evolution step, which is common in the majority of current approaches. Instead, it is able to derive more complete and accurate path information more efficiently from the global entropy spectrum.

Problems solved by technology

By comparison with invasive techniques, tractography measurements are indirect, difficult to interpret quantitatively, and error-prone.

Reconstruction of tissue fiber pathways from volumetric diffusion weighted magnetic resonance imaging (DW-MRI) data is an inherently ill-posed problem because the local (voxel) diffusion measurements are noisy and made on a scale significantly greater than the underlying fibers and, thus, there are a multitude of possible neural pathways between any two given points in the imaging volume that might be consistent with the experimental data.

These algorithms are “local” in the sense that the computations are done at each voxel and some small neighborhood around it and thus are not informed by the final path that is created, and thus are not capable of assessing the probability of the final path amongst all possible paths.

However, the DTI model is not sufficient to capture more realistic possibilities of complex fiber crossings needed for clinical applications.

While it has long been recognized that the most general nonparametric (model-free) approach is to measure the displacement probability density function or diffusion propagator directly, the natural extension of this to imaging wherein 3D Cartesian sampling of q-space is used to obtain the 3D displacement probability density function (dPDF) at each voxel, is prohibitively expensive from the standpoint of data acquisition.

However, this distinction between local and global estimation is artificial and limiting, since both the local (voxel EAP) information and the global structure (tracts) are from the same tissue, just seen at different scales.

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